The lowdown: Michael Moore’s controversial and passionate anti-Bush polemic, winner of the best picture prize at this year’s Cannes Film Festival.Let’s get this out of the way: “Fahrenheit 9/11” is a savagely partisan indictment of George W. Bush’s presidency. It pulls no punches and has nothing nice to say about the commander in chief, whom director and professional rabble rouser Michael Moore portrays as venal, flip and box-of-rocks dumb. Supporters of the president will find this reprehensible. Detractors of the president will rub their hands with glee. If this offends you, read no further. If you can’t help yourself, don’t say I didn’t warn you. The already infamous “Fahrenheit 9/11” begins with Bush’s dubious victory in 2000 and continues straight through to the present, which finds us in a war launched for reasons that, according to Moore, have everything to do with money, greed and connections (the true reasons for most wars, it must be said) and almost nothing to do with America’s alleged war on terrorism. Moore’s premise — much of which is gleaned from investigative reporter Craig Unger’s “House of Bush, House of Saud: The Relationship Between the World’s Two Most Powerful Dynasties” — follows: The president and his extended family enjoy deep-rooted, mutually beneficial business relationships with many wealthy Saudis. These include the house of bin Laden, of which Osama is the black sheep. It is these family and financial connections that have guided Bush’s actions since 9/11. They account for his intentionally inept handling of the war in Afghanistan, the fact that despite our sophisticated weaponry and intelligence-gathering abilities we’ve never been able to catch a 6-foot-5 Saudi diabetic living in a cave and finally, why, Moore contends, war against Iraq was essentially a smokescreen launched to steer national attention away from any Saudi involvement in terrorism. From a cinematic perspective, “Fahrenheit 9/11” is a confident, expansive and mostly polished piece of moviemaking. The editing is brisk and controlled, and Moore uses sound and music to terrific effect. In depicting 9/11, the screen goes black, while on the soundtrack we hear an enormous, molar-rattling crash, followed by the astonished cries of New Yorkers in the street. It’s a moving moment played with uncharacteristic restraint. Since his sometimes rambling Oscar-winning “Bowling for Columbine” Moore has grown as a filmmaker, and even a polemicist. His benign, Midwestern voice is ever-present in this film — guiding, questioning, explaining and connecting dots that, admittedly, seem a tad far apart. The viewer’s task here is to decide how much he wants to resist Moore’s apparent authority. His facts (already hotly contested by many conservative pundits) zip by like a speed skater in training: George Bush spent 42 percent of his pre-9/11 presidency on vacation; 6 or 7 percent of the United States is actually owned by Saudi Arabia. One is reminded of the old joke about statistics — why, 67 percent of them are made up on the spot! Still, Moore’s points are well-taken. While Moore’s voice is ever-present, the man himself is rarely on screen, an improvement over his camera-hogging habits of yore. There are a few trademark bits where the chump in the baseball cap pesters the powerful slimy guy in the suit, but they’re played mostly for much-needed comic relief. Near the end of the film, Moore and an Army recruiter approach members of Congress to ask whether they’d be interested in pressing their children join the military to help the cause in Iraq. Of course, he gets no takers. Despite Moore’s sometimes heavy-handed narration and tenuous theories, and a few segments in the second half where he loses focus (the movie’s about 10 minutes too long), this is a surprisingly disciplined movie. There are several moments when his snarkiness threatens to discredit his case. In discussing Bush’s alleged desertion from the military, the camera slowly closes in on the document that verifies this, over which we hear the immediately recognizable opening riff from Eric Clapton’s “Cocaine,” which induces the intended smirk. Mostly, though, Moore resists the cheap shot. The man should be forgiven for indulging himself by including an interview with Britney Spears waxing political. “Fahrenheit 9/11” is a huge, disturbing, sometimes funny, ultimately taxing movie. War is always hell, however we got there, and watching the ravages of war — there are many graphic images of injured Iraqis, and equally disturbing interviews with young American soldiers who weren’t quite prepared for what they found in Baghdad — will leave you feeling enraged, saddened, heart sick, manipulated or all of the above.In the end, one of the most damning images of Bush also is one of the quietest. On the morning of 9/11 the president visited an elementary school classroom in Florida. Shortly before entering the classroom, the first tower was hit. Bush elected to continue the visit. In a videotape shot by one of the teachers, he’s shown sitting on a little chair in front of the classroom. After a few moments, one of Bush’s people comes in to report that the second tower has been hit. The president just sits there flipping through a copy of “My Pet Goat.” Minutes pass. He does nothing. There’s every chance “Fahrenheit 9/11” will be a tempest in a teapot; after all “Spider-Man 2” opens in a matter of days. However, Moore’s lively diatribe has sparked fresh national debate on things that actually matter. For a brief and shining moment, we’re focused on thornier topics than whether J. Lo and Marc Anthony are really married, and the rest of the dross that normally serves as public debate, and for that he deserves our thanks.